Bimetallic contact element for electronic musical instrument



July 11, 1967 H G BAUER 3,330,916

BIMETALLIC coNTA cT ELEMENT FOR ELECTRONIC MUSICAL INSTRUMENT Original Filed Oct. 26, 1960 .7 d I a l 1% Z .30

54 INVENTOR. 7g .zgwardffieaefl Continuation of application Ser.

.ments whereby the above objects A structure in accord with the invention includes a tronic musical instrument; and a United States Patent 3 330 916 BIMETALLIC CONTACT ELEMENT FOR ELEC. TRONIC MUSICAL INSTRUMENT Howard G. Bauer, Corinth, Miss., assignor to The Wurlitzer Company, Chicago, 111., a corporation of Ohio No. 65,076, Oct. 26, 1960. This application July 27, 1964, Ser. No. 386,117

8 Claims. (Cl. 200-) ABSTRACT OF THE DISCLOSURE A switch for electronic musical instruments wherein the switch includes fixed and movable whisker-like contacts one of which is bimetal with a material of high flexural strength along a major portion thereof and with a contact portion of a material having high resistance to arcing and oxidation.

This application is a continuation of my prior application, Ser. No. 65,076, filed Oct. 26, 1960, now abandoned.

This invention relates generally to electronic musical instruments and especially to components for use in the electrical switches which are operated by the note sounding keys of such instruments.

In order to conserve space and in order to obtain relatively uncomplicated assemblies, the electrical contact elements used in electronic musical instruments commonly comprise simple sections of conductive wire, sometimes straight, sometimes configurated. Ordinarily, these wire or whisker-type contact elements are flexed longitudinally when engaging or engaged by other contact elements; and as is the case with any electrical contact elements, the wire contact elements of electronic musical instruments are subjected to electrical stresses upon the making or breaking of electrical contact.

Unfortunately, those materials displaying good resistance to arcing and to oxidation are not characterized by high flexural strength, and vice versa. Hence, the whiskertype contact elements heretofore used in electronic musical instruments have been beset with problems arising from flexural fatigue failure or from damage due to arcing.

Accordingly, a general object of the present invention is to provide a new and improved contact element for electronic musical instruments.

Another object of the invention is to provide an electrical contact element of the type described which combines high flexural strength with good resistance to areing and oxidation.

Yet another object of the invention is to provide an inexpensive, electrical contact element having long and useful service life in an electronic musical instrument.

Additional objects and features of the invention pertain to the particular structure, materials and arrange are attained.

fiexurally strong, conductive wire at one end to a mounting means adapted to be secured incorporated in an elecconductive wire of contact metal fixed in substantially coaxial relationship to the free end of the fiexurally strong wire to define a contact element adapted to be engaged by another contact element.

The invention, both to its structure and mode of operation, will be better understood by reference to the following disclosure and drawing forming a part thereof, wherein:

FIG. 1 is a side elevation-a1 view in partial cross-section of an electronic musical instrument keyboard incorporating a switch arrangement which employs contact elements 3,330,915 Patented July 11, 1967 constructed in accordance with the invention, the switch arrangement being illustrated in its normal or rest position, the section being taken along a central plane drawn through the electronic musical instrument;

FIG. 2 is a side elevational view taken along the same section used for FIG. 1 and being similar to the showing of FIG. 1 but illustrating the switch arrangement in its operating position;

FIG. 3 is an exploded and enlarged perspective view of the parts making up the contact element of the invention; and

FIG. 4 is an enlarged perspective view of an assembled contact element in accordance with the invention.

Referring now in detail to the drawing, especially to FIGS. 1 and 2, an electronic musical instrument key 10 of conventional construction is shown pivotally mounted to a balance rail 12 by means of a balance rail pin 14. The balance rail 12 is integrally joined to a keybed 16 that extends across the body of the electronic musical instrument. Advantageously, the keyboard end of key 10 is biased in a vertically upward direction by means of a tension spring 18 which is disposed between a bracket 20 that is secured to the rearward end of balance rail 12 and the rearward end of key 10.

In compliance with customary practice, a front plate 22 extends across the keyboard of the electronic musical instrument; and behind the plate 22 are disposed a number of electrical switches, each of the operating keys 10 being arranged with two or more of these switches. As shown, a switch arrangement indication generally by the numeral 24 is arranged with a circuit board 26 that provides electrical connections such as to the amplifiers and continuously operating oscillators customarily incorporated in an electronic musical instrument.

The switch 24 comprises an upper fixed contact 28, a lower fixed contact 30 and a movable contact 32, each of the contacts 28, 30 and 32 being mounted to the circuit board 26 and electrically connected to appropriate portions of the circuit carried thereby. A switch arm 34 is mounted to the key 10 in order to facilitate relocation of the movable contact 32 upon depression of the key. In addition, a suitably slotted guideboard 36 may be provided for establishing and maintaining proper positional relationship between the contacts 28, 30 and 32.

In somewhat similar manner, a switch arrangement indicated generally by the numeral 38 is situated generally between the front plate 22 and the switch arrangement 24, switch arrangement 38 being arranged for actuation of the percussion effects of the musical instrument notes if such effects are desirably incorporated. In the switch arrangement 38, a contact element 40 is afiixed to a switch arm 42, the switch arm 42 being, in turn, afiixed to the key 10. A pair of elongated, spaced-apart conductors 44 and 46 are mounted sandwiching the contact element 40, conductors 44 and 46 being specifically mounted to a channel element 48 by means of an insulating strip 50.

It is important to point out that the contact elements 28, 30 and 40 are straight wire or whisker-type contact elements; and as will become apparent from a comparison of FIGS. 1 and 2, the contact elements 28, 30 and 40 are flexed rather substantially in a longitudinal direction when engaged by the cooperating contact or conductive elements.

In accordance with the present invention, the contact elements 28, 30 and 40 are similarly constructed; and turning to FIGS. 3 and 4, the construction of contact element 28 will become apparent. There, the contact element 28 will be seen to include a fiexurally strong, conductive wire 52 desirably fashioned from an alloy of beryllium and copper. To one end of the wire 52 there "greater than the transverse is aflixed in substantially coaxial relationship a conductive wire 54 of contact metal, desirably an alloy of silver and platinum. As is particularly well shown in FIG. 4, the wires 52 and 54 are joined together by a butt weld 56.

In assembly, the free end of wire 52 is employed in mounting the contact element. So assembled, the wire 52 is capable of bearing the mechanical stresses applied to the contact in use, and the wire 54 is capable of bearing the electrical stresses applied to the contact whereby to resist damage due to oxidation and arcing incurred upon the making and breaking of electrical contact.

The contact 32 is advantageously arranged in either L- shape or U-shape in order to present a portion extending at right angles to the contacts 28 and 30. It is to be recognized that element 32 may be constructed with the flexing portion fashioned from flexurally strong wire such as the wire 52 and having the portion for making contact'with the elements 28 and 30 fashioned from contact wire such as the wire 54.

It is to be generally recognized that the wire used in the contact element 28, 30, 32 and 40 is fine wire on the 'order of 0.016 inch inv diameter;

The specific example herein shown and described should be considered as illustrative only. Various changes in structure m-ay occur in those skilled in the art; and such changes are to be understood as forming a part of this invention insofar as they fall within the spirit and scope of the appended claims.

' What is claimed is:

1. In a switch arrangement for electronic musical instruments, the combination comprising a pair of mutually engageable contacts with mounting and actuating means therefor and one of the mutually engageable contacts including atwo-part contact member including a discrete substantially straight, rod-like body element of electrically conductive and flexurally strong material, said body element having a compartatively substantial length and a comparatively small cross-section whereby to be flexible, the lengthof said body element being less'than the length of the contact required for'mutual engagement with the other contact, said one contact member further including a discrete substantially straight, rod-like element of contact alloy metal of the same small cross-section mechanically and electrically aflixed to one end of said body element of flexurally strong material in butting coaxial relation thereto to extend the length of said one contact with said element of contact metal into operative position for mutual engagement with the said other contact, relative movement of said one contact between open and closed position causing said body element of flexurally strong material to react flexibly and bear mechanical stresses appliedto said one contact, such flexible reaction being operative to change the eifective length of said one contact attendant upon the non-linearity produced upon flexing thereof, said element of contact metal bearing electrical stresses applied thereto and having an axial dimension beyond the body element appreciably dimension thereof whereby to accommodate the axial dimension of the element of contact metal to' minor misalignments with the said other contact and effect a wiping mutual engagement therewith as the eifectivelength of said one contact changes upon flexing thereof.

2. In a switch arrangement for an electronic muscial instrument, the combination comprising a plurality of switch assemblies each including cooperating and mutually engageable movable and substantially fixed contacts, mounting means between substantially fixed contacts, control key means carrying the movable contacts,

at least one contact of each assembly comprising atwopart contact member for cooperation with the other contact, said two-part contact member including a discrete substantially straight, rod-like body element of electrical monductive and flexurally strong material, said body element having a comparatively substantial length and a comparatively small cross-section whereby to be flexible, the length of said body element being less than the length of the contact member required for mutual engagement with'the said other contact, said contact member further including a discrete substantially straight, rod-like element of contact metal separately aflixed to one end of said body element of flexurally strong material to extend the length i of said contact member into operative position for mutual engagement with the said other contact, relative movement of said contacts between open and closed positions causing said body element of flexurally strong material to react flexibly and bear mechanical stresses applied to said contact member, such flexible reaction being operative to change the' effective length of said contact member attendant upon the non-linearity produced upon flexing thereof, said element of contact metal bearing electrical stresses applied thereto and having an axial dimension beyond the body element appreciably greater than the transverse dimension thereof whereby to accommodate the axial dimension of the element of contact metal to minor misalignments with the said other contact and effect a wiping mutual engagement therewith as the effective length of said contact member changes upon flexing thereof.

3. The combination according to claim 2, wherein the two-part contact member terms the movable contact.

4. The combination according to claim 2, wherein the two-part contact member forms the substantially fixed contact.

5. The combination according to claim 2 wherein said flexurallystrong material is an alloy of beryllium and copper and wherein said contact metal is an alloy of silver. 7

6. The combination according to claim 2 wherein said element of flexurally strong material and said element of contact metal are afiixed together in substantially coaxial relationship.

7. The combination according to claim 2, wherein the switch assemblies are arranged in pairs with the two-part contact member forming the movable contact for one pair and with two-part contact member forming the substantially fixed contact of the other pair.

8. The combination according to claim 2, wherein the rod-like element of contact metal is of the same small cross section as the body element and disposed in butting coaxial relation thereto.

References Cited UNITED STATES PATENTS 1,935,897 11/1933 Wise 200-166 X 2,501,164- 3/1950 Durst 200-166 X 2,653,199 9/1953 Brown et al 200-87 3,060,784 10/1962 Holt 200-166 X 3,201,853 8/1965 Howarth et al. 200-166 X 3,208,129 9/1965 Talbot et al. 200-166 X OTHER REFERENCES Websters Third New International Dictionary, Unabridged, page 476, col. 1.

ROBERT K. SCHAEFER, Primary Examiner. I. R. SCOTT, Assistant Examiner. 

1. IN A SWITCH ARRANGEMENT FOR ELECTRONIC MUSICAL INSTRUMENTS, THE COMBINATION COMPRISING A PAIR OF MUTUALLY ENGAGEABLE CONTACTS WITH MOUNTING AND ACTUATING MEANS THEREFOR AND ONE OF THE MUTUALLY ENGAGEABLE CONTACTS INCLUDING A TWO-PART CONTACT MEMBER INCLUDING A DISCRETE SUBSTANTIALLY STRAIGHT, ROD-LIKE BODY ELEMENT OF ELECTRICALLY CONDUCTIVE AND FLEXURALLY STRONG MATERIAL, SAID BODY ELEMENT HAVING A COMPARTATIVELY SUBSTANTIAL LENGTH AND A COMPARATIVELY SMALL CROSS-SECTION WHEREBY TO BE FLEXIBLE, THE LENGTH OF SAID BODY ELEMENT BEING LESS THAN THE LENGTH OF THE CONTACT REQUIRED FOR MUTUAL ENGAGEMENT WITH THE OTHER CONTACT, SAID ONE CONTACT MEMBER FURTHER INCLUDING A DISCRETE SUBSTANTIALLY STRAIGHT, ROD-LIKE ELEMENT OF CONTACT ALLOY METAL OF THE SAME SMALL CROSS-SECTION MECHANICALLY AND ELECTRICALLY AFFIXED TO ONE END OF SAID BODY ELEMENT OF FLEXURALLY STRONG MATERIAL IN BUTTING COAXIAL RELATION THERETO EXTEND THE LENGTH OF SAID ONE CONTACT WITH SAID ELEMENT OF CONTACT METAL INTO OPERATIVE POSITION FOR MUTUAL ENGAGEMENT WITH THE SAID OTHER CONTACT, RELATIVE MOVEMENT OF SAID ONE CONTACT BETWEEN OPEN AND CLOSED POSITION CAUSING SAID BODY ELEMENT OF FLEXURALLY STRONG MATERIAL TO REACT FLEXIBLY AND BEAR MECHANICAL STRESSES APPLIED TO SAID ONE CONTACT, SUCH FLEXIBLE REACTION BEING OPERATIVE TO CHANGE THE EFFECTIVE LENGTH OF SAID ONE CONTACT ATTENDANT UPON THE NON-LINEARITY PRODUCED UPON FLEXING THEREOF, SAID ELEMENT OF CONTACT METAL BEARING ELECTRICAL STRESSES APPLIED THERETO AND HAVING AN AXIAL DIMENSION BEYOND THE BODY ELEMENT APPRECIABLY GREATER THAN THE TRANSVERSE DIMENSION THEREOF WHEREBY TO ACCOMODATE THE AXIAL DIMENSION OF THE ELEMENT OF CONTACT METAL TO MINOR ALIGNMENTS WITH THE SAID OTHER CONTACT AND EFFECT A WIPING MUTUAL ENGAGEMENT THEREWITH AS THE EFFECTIVE LENGTH OF SAID ONE CONTACT CHANGES UPON FLEXING THEREOF. 